1211662566 has 72 divisors (see below), whose sum is σ = 2785170960. Its totient is φ = 380637792.

The previous prime is 1211662549. The next prime is 1211662589. The reversal of 1211662566 is 6652661121.

1211662566 is a `hidden beast` number, since 1 + 21 + 1 + 6 + 625 + 6 + 6 = 666.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1211662566.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1708620 + ... + 1709328.

It is an arithmetic number, because the mean of its divisors is an integer number (38682930).

Almost surely, 2^1211662566 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1211662566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1392585480).

1211662566 is an abundant number, since it is smaller than the sum of its proper divisors (1573508394).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1211662566 is a wasteful number, since it uses less digits than its factorization.

1211662566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1018 (or 996 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 1211662566 is about 34808.9437644982. The cubic root of 1211662566 is about 1066.0900668620.

The spelling of 1211662566 in words is "one billion, two hundred eleven million, six hundred sixty-two thousand, five hundred sixty-six".